Prepare for 0.17.0 release (open-telemetry#698)

Prepare for v0.16.0 release (open-telemetry#612)

datadog: prepare for v0.3.1 patch release (open-telemetry#582) (open-…

…telemetry#584)

Prepare for v0.15.0 release (open-telemetry#572)

Prepare for 0.14.0 release (open-telemetry#548)

jaeger: prepare for 0.12.1 release (open-telemetry#503)

Prepare for v0.13.0 release (open-telemetry#470)

Prepare for v0.12.0 release (open-telemetry#433)

Prepare for v0.11.2 release (open-telemetry#408)

Prepare for v0.11.1 release (open-telemetry#406)